what size plants?

I never do it and I have yet to lose one. Even the new weakling varieties. However if you have that problem then maybe you should

nevermore--I think the pots are about a 2 or 3 quart size. The plants are between 14 and 18" tall.

In my experience with Echinacea, when you do disbud, the plant goes into hyperdrive to produce more flowers. You could always allow it to bloom and remove the spent blooms quickly. You also have a great opportunity to experiment. I would plant one and leave it alone and enjoy the flowers and disbud the other one and plant and see if you get better results with one method over the other.

I believe that terra nova article (and others) are for plants that are not to far out of the plug stage. So you should be fine to let yours bloom.

The only exception to that is if the plants you purchased have only a single growth point coming out of the soil. Regardless of how bushy, healthy, and floriferous that single stem is... I would advise, besides to always check the plant before you buy one of the new echs, is to cut all the blooms in order to try and force the plant to add more basal growth points before the end of the season. The single stem plants will never make it through winter. Certain varieties seem more apt to have this issue.

I do disbud many perennials and all clematis before planting them but I often will keep them in their pots and enjoy the flowers before cutting them back.